Electronic devices are commonly used for communication and entertainment purposes. Examples of these devices include cellular phones, smartphones, tablet computers, audio players, video players, cameras, portable computers, two-way radios, GPS receivers, other electronic devices, or combinations thereof. Many of these devices communicate with other devices or systems using wireless communication. As the reliance upon these types of electronic devices increases, the reliance upon wireless communication also increases. In addition, there is an increasing need to protect these devices from damage, particularly with respect to mobile electronic devices which are often even more susceptible to being damaged, being dropped, being exposed to wet or dirty operating environments, and/or being exposed to damaging weather conditions.
Electronic devices also tend to become smaller over time, yet often perform more functions and/or increasingly complex functions. Some of these functions require transmission and reception of wireless signals including voice information, data signals, and/or navigation information. Examples of voice and data signals may include 2G, 3G, and/or 4G signals such as GSM, CDMA, UMTS/W-CDMA, 1x-RTT, EVDO, or LTE modulated signals, and/or other types of signals. These signals may also include WiFi or Bluetooth signals. Examples of navigation signals may include global positioning satellite (GPS) data. In many situations, electronic devices are mobile communication devices used to communicate data to/from a cellular base station.
The antennas an electronic device uses to transmit and receive signals must support a broad range of frequencies (e.g., have sufficient bandwidth) yet remain embedded, conformal, and/or predominantly internal to the electronic device. There are often significant limitations placed on the amount of physical volume an internal or native electronic device antenna can occupy in the electronic device. However, antennas generally need more volume to support more bandwidth efficiently.
The volume and location limitations placed on internal or native antennas in compact electronic devices often results in lower efficiency, lower gain, and/or reduced instantaneous bandwidth. One or more of these factors results in weaker signals delivered to the electronic device receive circuitry from the antenna and/or weaker signals radiated by the antenna to a receiving device. The result to some end users is phone calls of poor quality, dropped calls, lower data transfer rates, lower battery life due to increase transmit power, and/or reduced transmission distances. Further, multipath effects, fades, and/or shadowing from a cellular base station can have a more pronounced effect on electronic devices with volume restricted antennas. While techniques such as active tuning can be employed to overcome some of these limitations, it is often done so at the expense of complexity, additional circuitry, and/or higher component cost.
For many electronic device users, the restrictions placed on antennas do not observably or noticeably impact the quality of service due to their proximity to a cellular base station or other communication node. For some users who live, work, and/or travel further from cellular base stations, or who have cellular service with a service provider with a more sparsely-populated cellular tower network, the result may be more frequently dropped calls, decreased call quality, slower data transfer speeds, reduced device battery life, and/or a generally lower quality of service. Many of these users would greatly benefit from a device that overcomes some or all of the limitations of the volume-restricted antennas found inside many electronic devices, mobile electronic devices, mobile computing devices, mobile phones, cellular phones, and/or smartphones.
Further compounding the volume restrictions placed on electronic devices is the detuning and attenuation effects of a user's hands and/or head that may be near the electronic device. Measurements made using a Cellular Telecommunication Industry Association (CTIA) certifiable over-the-air (OTA) cellular range confirm that many mobile electronic devices exhibit near omnidirectional radiation in the azimuth plane (the plane with an axis parallel to the long axis of the mobile device) when in free-space (not held by or attached to a user). However, when held by a user, radiation from the devices becomes markedly directional (and of lower overall efficiency) due to interactions with the user's body.
Some mobile electronic devices are designed to accommodate a majority of users holding the device in their right hand. This accommodation is accomplished by placing the antenna(s) such that a right-handed user interferes with the radiated and received signal less than a left handed user. Furthermore, worldwide government regulatory agencies (e.g., the United States Federal Communications Commission (FCC)) place restrictions on the amount of power permitted to be absorbed by different parts of the human body with different surface area over periods of time. In order to accommodate these types of Specific Absorption Rate (SAR) requirements, manufacturers of devices will often reduce the output power when proximity to a user is sensed. However, these techniques may compound the signal strength and quality of service issues even further.
A common technique to overcome both body attenuation and detuning effects, as well as SAR restrictions, is to place the primary transmit antennas near the bottom of the mobile electronic device. The advantages are at least two-fold. First, the antennas are not directly against the user's head due to the typical natural spacing between the bottom of the electronic device and the user's face or jaw when conducting a voice communication using the device. Second, there is usually a small air gap between the mobile device and the user's hand due to the natural cupping effect of the hand while holding the mobile electronic device. Despite the elaborate engineering involved in the design and placement of cellular antennas for mobile devices, certain limitations on efficiency exist because of body-phone interaction, limited volume, reduced instantaneous bandwidth, and/or poor gain.
Some devices extend the range of a mobile electronic device (e.g., from the node to which it communicates) as well as simultaneously shield the user from harmful radiation. For example, some devices shroud the internal or native antenna to redirect radiation away from the user and enhance or increase the amount of energy directed toward a receiving device. Some devices include an additional antenna that is wired directly into the transmit/receive module of the electronic device and may also include the aforementioned shroud to direct energy away from the user. Some devices may include an add-on module to a mobile electronic device which includes a hard-wired or direct electrical connection that connects directly into the transmit/receive module of the device (e.g., into a plug or socket where the native or internal antenna would typically connect). The direct electrical connection feeds a directive antenna and reflective ground plane on the back-side of the device in order to direct radiation away from the user.
Other approaches redirect or steer energy away from the user's head through coupling to the internal or native antenna and redirecting the radiation in a direction that is generally away from the user. In general, the coupling to the internal antenna may be through parasitic means. These devices then parasitically couple to a set of radiation directors or redirectors, and finally to a re-radiation antenna inside the mobile electronic device. While the net result of these solutions may be to reduce radiation direction toward the user, the serial losses which arise from multiple parasitic couplings yields a significant net loss in transmitted power. Even a well-designed and well-tuned parasitic coupler can suffer from greater than 2 decibels of loss, which may represent a loss of over 30% of the signal energy in some cases. Each coupling stage is susceptible to losses of this magnitude which can result in significant overall signal strength degradations.
A user of a mobile electronic device may be walking, driving, or otherwise moving with respect to one or more base stations or nodes the device is communicating with. The user often has no knowledge of the location of the base station or node with respect to his or her position. The user often has no facility or resources to aim or orient the mobile electronic device relative to the base station in a manner to improve the communications. When using a device that redirects the energy of the mobile electronic device, the orientation of the user and/or the electronic device may become even more critical because the energy radiated in some directions has been intentionally reduced and/or the overall energy in all directions may have been reduced significantly. Energy that is redirected away from the user toward the backplane of the device represents a dearth of energy toward a base station that could, with equal probability, be disposed at any direction azimuthally with respect to the user (that is, in the plane whose vertical axis is coincident with the vertical axis of the user). Since energy is being diverted away from a significant portion of the spherical volume around the electronic device, the statistical net result of this approach is that for a randomly oriented user, dropped calls can statistically occur with significantly higher probability.
It is well known to those skilled in the art that the power density as a function of angle with respect to a mobile device is highly perturbed and modified when the device is held by a user in the hand or in the hand and next to the head. (M. Pelosi, et al, “Antenna Proximity Effects for Talk and Data Modes in Mobile Phones,” IEEE Antennas and Propagation Magazine, 52, 3, June 2010; J. Toftgard, et al, “Effects on Portable Antennas of the Presence of a Person,” IEEE Transactions on Antennas and Propagation, AP-41, 6, June 1993; J. Krogerus, et al, “Effect of the Human Body on Total Radiated Power and the 3-D Radiation Pattern of Mobile Handsets,” IEEE Transactions on Instrumentation and Measurement”, IMS-56, December 2007. In other words, the Total Radiated Power (TRP) and Total Isotropic Sensitivity (TIS) antenna pattern of a mobile device, which are exclusively and largely (respectively) functions of the antenna pattern, are dramatically perturbed through detuning and absorption based on interaction with the human body. It has been shown that over 11 decibels of net loss may occur through both detuning and absorption when a user holds a mobile electronic device, meaning that in some cases as much as 90% of the power transmitted by the mobile electronic device may be lost.
Therefore, apparatuses, techniques, systems, and methods are introduced herein to improve signal strength for an electronic device and enhance the quality of service for a user of the electronic device by enhancing the wireless signal strength delivered to/from the electronic device through its native or internal antennas. Quality of service enhancements may result in reduction of dropped calls, range extension to a node, increases in data transfer rate to/from the device, lower battery drain to achieve a threshold level of service, higher power density level delivered to the RF processing circuitry of the electronic device while the device is in receive mode, and/or higher power density transmitted to a receiving node when the electronic device is in transmit mode.
The apparatuses, techniques, systems, and methods introduced herein may improve quality of service while also preserving or enhancing the performance of an electronic device by preserving some or all of the omni-directionality in the energy transmitted from and received by the electronic device even while being held by the user and/or placed next to the head. This may be achieved while also meeting FCC and/or other governmental regulatory limits on SAR.